When a stress is applied to a piezoelectric element formed of a piezoelectric ceramic material to minutely vibrate the piezoelectric element, an electromotive force is generated. A piezoelectric generating element is an element utilizing the electromotive force generated described above, and various types of piezoelectric generating elements have conventionally been proposed.
For example, Patent Document 1 proposes an element for piezoelectric generation comprising a piezoelectric element having a unimorph structure in which a rectangular plate-shaped single piezoelectric element having electrodes on both surfaces thereof is bonded to an elastic plate, or having a bimorph structure or a stacked structure in which at least two or more piezoelectric elements are bonded with an elastic plate interposed therebetween, wherein the piezoelectric element has one end as a fixed end and the other end as a free end, a certain weight is attached to the free end, and the entire element is sealed in a container with a space in which the free end is allowed to deflect to a certain degree.
In Patent Document 1, one end of the piezoelectric element is fixed, the other (free) end is provided with the weight, an external force is applied to the piezoelectric element to vibrate it using the inertial force of the weight, and thereby power is generated.
Further, Patent Document 2 proposes a piezoelectric ceramic element for power generation obtained by mixing ceramic materials for a piezoelectric element such as lead titanate and lead zirconate and sintering the mixture, wherein a fiber material having a melting point higher than the sintering temperature and having a high tensile strength is mixed as a bonding agent for preventing cracks, in addition to particle powders of various types of ceramic materials constituting the element.
In Patent Document 2, the fiber material having a melting point higher than the sintering temperature and having a high tensile strength is mixed into between ceramic particles. This prevents the piezoelectric ceramic element from being broken when vibration is applied thereto.